| As members of the common digestive tract cancer, both gastric cancer and colorectal cancer are great threats to human. According to the global cancer statistic data of2008, gastric cancer and colorectal cancer are the fifth and the second frequently diagnosed cancer respectively. And they are the second and the third leading cause of cancer death respectively. Despite the improved diagnostic and therapeutic methods, tumor invasion and metastasis are still great threats to the patients. According to the research data, with the depth of tumor infiltration increasing from T1-T4, the5-year survival rate of the gastric cancer patients decreased from about85%to about10%. And with the increasing number of lymph node metastasis from N0-N3, the5-year survival rate of gastric cancer patients decreased from about80%to about20%. Research data also showed that lymph node metastasis was the most important prognostic indicator of the T3patients with colorectal cancer. With the increasing lymph node metastasis, the3-year survival rate declined sharply from80%to30%. Therefore, it is meaningful to identify invasion and metastasis-related genes in gastric and colorectal cancer. It will help us not only to explain the invasion and metastasis mechanisms in both cancer, but also to find new therapeutic targets to improve the diagnosis and treatment.The emergence and development of Chip and proteomics technology greatly accelerated the progress of cancer research. By using these efficient technologies, researchers could easily identify a mass of genes and proteins that participated in a signaling pathway or a certain physiological phenomena.CCDC134was a novel gene that found to be involved in the Elk signal pathway by using the cell microarray system. An early study revealed that CCDC134acted as an inhibitor of MAPK pathway by negatively regulating the phosphorylation of Erk and JNK/SAPK without affecting the phosphorylation of p38, suggesting that CCDC134might play an important role in maintaining the homeostasis of MAPK pathway. Since many studies have demonstrated that the aberrant activation of MAPK pathway was closely correlated with the metastasis and poor clinical outcome of gastric caner, we speculated that CCDC134might be involved in these processes. In this study, we found that CCDC134expression significantly reduced in gastric cancer tissues compared with normal tissues (P<0.001) and lesion tissues (P<0.001). However, we haven't observed the expression difference between normal and lesion tissues (P=0.842). In vitro, transient transfection of CCDC134-specific siRNA significantly promoted the migration and invasion of both normal gastric epithelial cell line GES-1and gastric cancer cell line AGS cells. Further analysis revealed that the attenuated expression of CCDC134promoted the activation of Erkl/2and JNK/SAPK, but had no effect on the activation of p38. Besides, CCDC134-RNAi could induce the expression of MMP-2, MMP-9and p-FAK-Ser910. These proteins are key molecules involved in regulating cell migration and invasion.UCHL1was identified to be closely related to the lymph node metastasis in our previous work by using proteomics technology. In this study, we transfected pcDNA3.1/UCHL1and pcDNA3.1/UCHL1-C90S mutant into HCT8cells. Then the changes of cell proliferation, migration and invasion in these stable transfectants were examined both in vitro and in vivo. In vitro, we found that re-expression of UCHL1significantly promoted the proliferation, migration, and invasion capabilities of HCT8cells (P<0.05, P<0.05, P<0.05). However, these functions were abolished in UCHL1-C90S, a mutant with impaired deubiquitinase activity. This result indicated that the malignant phenotype promoting founction of UCHL1depended on its deubiquitinating activity. In vivo, we found that the re-expression of UCHL1significantly promoted tumorigenesis, lymph node metastasis and lung metastasis of HCT8cells (P<0.05, P<0.05, P<0.05). Further study indicated that UCHL1could up-regulate β-catenin by enhancing its stability, depending on its deubiquitinating activity. The accumulation of β-catenin in cytoplasm resulted in increased β-catenin translocation into cell nucleus, then consequently activated the β-catenin/TCF pathway and induced the expression of cyclin D1and uPA. These observations imply that UCHL1may contribute to colon cancer progression by activating the β-catenin/TCF pathway through its deubiquitinating activity. In order to identify the candidate proteins that regulated by UCHL1, a proteomic analysis was performed. Nine differentially expressed proteins were identified. These nine proteins expressed differentially not only between HCT8/pcDNA3.1and HCT8/UCHL1, but also between HCT8/UCHL1and HCT8/UCHL1-C90S. Among these9proteins,7were up-regulated by UCHL1, and2were down-regulated by UCHL1. And the mutant, UCHL1-C90S had no effect on the expression of these9proteins.In this study, we disclosed the function of CCDC134in gastric cancer, and the function of UCHL1in colon cancer, and provided clues to find new diagnostic and therapeutic targets for gastric cancer and colon cancer.
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